A number of tools are commercially available for extracting rings, bushings or other inserts which are tightly fitted within a confined recessed area. A particular example of an insert which must, on occasion, be extracted is the valve seat within a cylinder head on an internal combustion engine. Typically, the existing pullers have jaws, usually two or three jaws, which work with the force created by either a slide hammer or a screw. The jaws are clamped against the part to be removed with a screw/bolt system, then the force is applied to the puller to remove the part.
Several difficulties can be experienced by the users of such pullers. Among these problems is the loosening of the jaws as a result of the application of force, which may be applied as either a rapid strike of a hammer or as a slow compression by turning the screw. This results in repeated interruption of the process to re-tighten the pressure of the jaws on the part. Such interruptions can be particularly problematic when the location of the insert to be removed is difficult to reach and the angle of approach is awkward. The size of many pullers compounds the difficulties experienced in hard-to-reach places.
Another disadvantage of existing pullers is that they are easily thrown off-balance when the force is applied, resulting in the majority of the force being applied to one jaw only. This can either cause the jaw to break, or can pull the insert out at an angle. As with the frequent loosening of the jaws, they must be repositioned repeatedly during the operation before the insert is completely extracted.
Conventional pullers are usually heavy and bulky due to the length of the threaded shaft of the screw-type puller or due to the size of the slide hammer itself in the impact-type puller.
In order to avoid damaging the housing from which the insert is being removed, a spacer ring is often used to rest on the ring or other insert to be removed. This "blinds" the operator, preventing visual control of how the jaws clamp the insert.
Methods of extracting press fitted valve inserts (valve seats) in engine cylinder head include: 1) metal turning, where the valve insert is machined out of the cylinder head. This method is time consuming and expensive, but does not damage the housing in the cylinder head. 2) Welding a cord inside of the valve seats to loosen the seat out of its housing when the metal cools down and retracts. This process is also time consuming and may cause deterioration of the surrounding surfaces by distributing slag around the work site. To avoid this damage, the user must protect the surrounding surfaces, especially the valve guides in the cylinder head. 3) Using conventional pullers as described above, which is inefficient and time consuming. 4) Inserting a lever inside of the ring or insert to lift it out of the housing. Commonly, the insert will come out at an angle, damaging the housing. If the housing is damaged, it will have to be machined to removed the damage, and the resulting larger diameter requires the use of repair inserts-an insert which is of a non-standard size.